I am planning to run many full-year simulations of CMAQv5.3.1 for the CONUS at 12km, and my preferred chemical mechanism is CB6_ae7 as it is believed to run faster than SAPRC07. However, I heard recently that SAPRC07 incorporates multiphase chemistry while CB6_ae7 does not, and this may impact Southeast US PM2.5 performance in CMAQ. I was wondering if there is a way to incorporate multiphase chemistry in CB6_ae7 in CMAQv5.3.1?
The CB6 mechanism as implemented in CMAQ is documented in Luecken et al. (2019). Details are in section 2 of that paper; heterogeneous reactions are described briefly in section 2.3, and in the article supplement.
If that is not sufficiently detailed to answer your question, then please provide more specifics for your application.